Chapter 8- Lecture Outline

Question 1

The Energy of Life

Answer 1

The living cell is a miniature chemical factory where thousands of reactions occur
The cell extracts energy stored in sugars and other fuels and applies energy to perform work
Some organisms even convert energy to light, as in bioluminescence

Question 2

_______________ is the totality of an organism’s chemical reactions
Metabolism is an emergent property of life that arises from orderly interactions between molecules
Organization of the Chemistry of Life into Metabolic Pathways

Answer 2

Metabolism

Question 3

A metabolic pathway begins with a specific molecule and ends with a product

Answer 3

Each step is catalyzed by a specific enzyme

Question 4

______________________ release energy by breaking down complex molecules into simpler compounds

Answer 4

Catabolic pathways

Question 5

________________________ the breakdown of glucose

in the presence of oxygen, is an example of a pathway of catabolism

Answer 5

Cellular respiration,

Question 6

_____________ consume energy to build complex molecules from simpler ones
The synthesis of protein from amino acids is an example of anabolism

Answer 6

Anabolic pathways

Question 7

__________ is the study of how energy flows through living organisms
Forms of Energy

Answer 7

Bioenergetics

Question 8

__________s the capacity to cause change

Energy exists in various forms, some of which can perform work

Answer 8

Energy

Question 9

__________________ is energy associated with motion
__________________: is kinetic energy associated with random movement of atoms or molecules
__________________ is energy that matter possesses because of its location or structure
______________ is potential energy available
for release in a chemical reaction

Answer 9

Kinetic energy

Heat (thermal energy)
Potential energy
Chemical energy

Question 10

Energy can be converted from one form to another

Answer 10

but it can be neither created nor destroyed

Question 11

___________________
According to the first law of thermodynamics, the energy of the universe is constant
Energy can be transferred and transformed,
but it cannot be created or destroyed
The first law is also called the principle of conservation of energy
Figure 8.3

Answer 11

The First Law of Thermodynamics

Question 12

___________________
During every energy transfer or transformation, some energy is unusable, and is often lost
as heat
According to the second law of thermodynamics
Every energy transfer or transformation increases the entropy

Answer 12

The Second Law of Thermodynamics

Question 13

occur without energy input; they can happen quickly or slowly
For a process to occur without energy input,
it must increase the entropy of the universe

Answer 13

Spontaneous processes

Question 14

Cells create ordered structures from less ordered materials

Organisms also replace ordered forms of matter and energy with less ordered forms

Answer 14

Energy flows into an ecosystem in the form of light and exits in the form of heat

Question 15

The evolution of more complex organisms does not violate the second law of thermodynamics

Answer 15

Entropy (disorder) may decrease in an organism, but the universe’s total entropy increases

Question 16

Biologists want to know which reactions occur spontaneously and which require input of energy
To do so, they need to determine energy changes that occur in chemical reactions

Answer 16

Free-Energy Change, G

Question 17

A living system’s free energy is energy that can do work when temperature and pressure are uniform, as in a living cell

Answer 17

free energy

Question 18

The change in free energy (∆G) during a process is related to the change in enthalpy, or change in total energy (∆H), change in entropy (∆S), and temperature in Kelvin units (T)

Answer 18

∆G = ∆H - T∆S

Question 19

Only processes with a negative ∆G are spontaneous
Spontaneous processes can be harnessed to perform work
Free Energy, Stability, and Equilibrium
Free energy is a measure of a system’s instability, its tendency to change to a more stable state

Answer 19

During a spontaneous change, free energy decreases and the stability of a system increases
Equilibrium is a state of maximum stability
A process is spontaneous and can perform work only when it is moving toward equilibrium

Question 20

Free Energy and Metabolism

The concept of free energy can be applied to the

Answer 20

chemistry of life’s processes

Question 21

___________ proceeds with a net release of free energy and is spontaneous
____________________ absorbs free energy from its surroundings and is nonspontaneous

Answer 21

An exergonic reaction

An endergonic reaction

Question 22

A cell does three main kinds of work

Answer 22

Chemical
Transport
Mechanical

Question 23

To do work, cells manage energy resources by __________________ the use of an exergonic process to drive an endergonic one

Answer 23

energy coupling,

Question 24

ATP (adenosine triphosphate) is the cell’s energy shuttle

Answer 24

ATP is composed of ribose (a sugar), adenine

(a nitrogenous base), and three phosphate groups

Question 25

The bonds between the phosphate groups of ATP’s tail can be broken by hydrolysis
Energy is released from ATP when the terminal phosphate bond is broken

Answer 25

This release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves
How the Hydrolysis of ATP Performs Work

Question 26

The three types of cellular work (mechanical, transport, and chemical) are powered by the hydrolysis of ATP

Answer 26

In the cell, the energy from the exergonic reaction of ATP hydrolysis can be used to drive an endergonic reaction

Question 27

The reactant that an enzyme acts on is called
the enzyme’s substrate
The enzyme binds to its substrate, forming an enzyme-substrate complex

Answer 27

The reaction catalyzed by each enzyme is

very specific

Question 28

is the region on the enzyme

where the substrate binds

Answer 28

The active site

Question 29

of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction

Answer 29

Induced fit

Question 30

in the Enzyme’s Active Site
In an enzymatic reaction, the substrate binds to the active site of the enzyme
The active site can lower an EA barrier by
Orienting substrates correctly
Straining substrate bonds
Providing a favorable microenvironment

Answer 30

Catalysis

Question 31

Each enzyme has an optimal temperature in which it can function

Answer 31

Each enzyme has an optimal pH in which it can function

Optimal conditions favor the most active shape for the enzyme molecule

Question 32

Cofactors are nonprotein enzyme helpers
Cofactors may be inorganic (such as a metal in ionic form) or organic
An organic cofactor is called a coenzyme
Coenzymes include vitamins
Enzyme Inhibitors

Answer 32

Competitive inhibitors bind to the active site
of an enzyme, competing with the substrate
Noncompetitive inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective
Examples of inhibitors include toxins, poisons, pesticides, and antibiotics

Question 33

The Evolution of Enzymes
Enzymes are proteins encoded by genes
Changes (mutations) in genes lead to changes
in amino acid composition of an enzyme

Answer 33

Altered amino acids in enzymes may result in novel enzyme activity or altered substrate specificity
Under new environmental conditions a novel
form of an enzyme might be favored
For example, six amino acid changes improved substrate binding and breakdown in E. coli

Question 34

Chemical chaos would result if a cell’s metabolic pathways were not tightly regulated
A cell does this by switching on or off the genes that encode specific enzymes or by regulating
the activity of enzymes
Allosteric Regulation of Enzymes

Answer 34

Allosteric regulation may either inhibit or stimulate an enzyme’s activity
Allosteric regulation occurs when a regulatory molecule binds to a protein at one site and
affects the protein’s function at another site
Allosteric Activation and Inhibition

Question 35

______________ is a form of allosteric regulation
that can amplify enzyme activity
One substrate molecule primes an enzyme to act on additional substrate molecules more readily
Cooperativity is allosteric because binding by a substrate to one active site affects catalysis in a different active site
Feedback Inhibition

Answer 35

Cooperativity

Question 36

In feedback inhibition, the end product of a metabolic pathway shuts down the pathway
Feedback inhibition prevents a cell from wasting chemical resources by synthesizing more product than is needed
Figure 8.21

Answer 36

Localization of Enzymes Within the Cell
Structures within the cell help bring order to metabolic pathways
Some enzymes act as structural components
of membranes
In eukaryotic cells, some enzymes reside in specific organelles; for example, enzymes for cellular respiration are located in mitochondria